[net] dns/dnsmessage: add boundary check in unpackSVCBResource
Gerrit Bot (Gerrit)
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Commit message
dns/dnsmessage: add boundary check in unpackSVCBResource
Currently, bodyEnd is calculated using the length parameter from the resource header without verifying if it exceeds the physical capacity of the msg buffer. If a malformed record provides a length that exceeds the buffer, it bypasses the first-pass parameter validation and causes an out-of-bounds slice during the second-pass copy operation.
Adding a check against len(msg) aligns this function with the boundary enforcement used throughout the rest of the package.
Change diff
diff --git a/dns/dnsmessage/svcb.go b/dns/dnsmessage/svcb.go
index 4840516..3eef598 100644
--- a/dns/dnsmessage/svcb.go
+++ b/dns/dnsmessage/svcb.go
@@ -189,6 +189,10 @@
paramsOff := off
bodyEnd := off + int(length)
+ if bodyEnd > len(msg) {
+ return SVCBResource{}, errResourceLen
+ }
+
var err error
if r.Priority, paramsOff, err = unpackUint16(msg, paramsOff); err != nil {
return SVCBResource{}, &nestedError{"Priority", err}
Change information
- M dns/dnsmessage/svcb.go
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Gopher Robot (Gerrit)
Gopher Robot added 1 comment![]( "Open in Gerrit")
I spotted some possible problems with your PR:
1. You have a long 343 character line in the commit message body. Please add line breaks to long lines that should be wrapped. Lines in the commit message body should be wrapped at ~76 characters unless needed for things like URLs or tables. (Note: GitHub might render long lines as soft-wrapped, so double-check in the Gerrit commit message shown above.)
2. You usually need to reference a bug number for all but trivial or cosmetic fixes. For the net repo, the format is usually 'Fixes golang/go#12345' or 'Updates golang/go#12345' at the end of the commit message. Should you have a bug reference?
Please address any problems by updating the GitHub PR.
When complete, mark this comment as 'Done' and click the [blue 'Reply' button](https://go.dev/wiki/GerritBot#i-left-a-reply-to-a-comment-in-gerrit-but-no-one-but-me-can-see-it) above. These findings are based on heuristics; if a finding does not apply, briefly reply here saying so.
To update the commit title or commit message body shown here in Gerrit, you must edit the GitHub PR title and PR description (the first comment) in the GitHub web interface using the 'Edit' button or 'Edit' menu entry there. Note: pushing a new commit to the PR will not automatically update the commit message used by Gerrit.
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Gopher Robot (Gerrit)
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ISMAIL GAMAL (Gerrit)
ISMAIL GAMAL added 1 comment![]( "Open in Gerrit")
I spotted some possible problems with your PR:
1. You have a long 343 character line in the commit message body. Please add line breaks to long lines that should be wrapped. Lines in the commit message body should be wrapped at ~76 characters unless needed for things like URLs or tables. (Note: GitHub might render long lines as soft-wrapped, so double-check in the Gerrit commit message shown above.)
2. You usually need to reference a bug number for all but trivial or cosmetic fixes. For the net repo, the format is usually 'Fixes golang/go#12345' or 'Updates golang/go#12345' at the end of the commit message. Should you have a bug reference?Please address any problems by updating the GitHub PR.
When complete, mark this comment as 'Done' and click the [blue 'Reply' button](https://go.dev/wiki/GerritBot#i-left-a-reply-to-a-comment-in-gerrit-but-no-one-but-me-can-see-it) above. These findings are based on heuristics; if a finding does not apply, briefly reply here saying so.
To update the commit title or commit message body shown here in Gerrit, you must edit the GitHub PR title and PR description (the first comment) in the GitHub web interface using the 'Edit' button or 'Edit' menu entry there. Note: pushing a new commit to the PR will not automatically update the commit message used by Gerrit.
For more details, see:
- [how to update commit messages](https://go.dev/wiki/GerritBot/#how-does-gerritbot-determine-the-final-commit-message) for PRs imported into Gerrit.
- the Go project's [conventions for commit messages](https://go.dev/doc/contribute#commit_messages) that you should follow.
(In general for Gerrit code reviews, the change author is expected to [log in to Gerrit](https://go-review.googlesource.com/login/) with a Gmail or other Google account and then close out each piece of feedback by marking it as 'Done' if implemented as suggested or otherwise reply to each review comment. See the [Review](https://go.dev/doc/contribute#review) section of the Contributing Guide for details.)
Done. Wrapped line lengths. There is no linked bug number in order to avoid publicly disclosing the crash vectors prior to the patch.
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Gerrit Bot (Gerrit)
Gerrit Bot uploaded new patchset![]( "Open in Gerrit")
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Sean Liao (Gerrit)
Sean Liao added 1 comment![]( "Open in Gerrit")
is this something that can easily be tested?
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ISMAIL GAMAL (Gerrit)
ISMAIL GAMAL added 1 comment![]( "Open in Gerrit")
is this something that can easily be tested?
Yes, I have just amended the commit to include TestSVCBUnpackOutOfBounds in svcb_test.go.
The test feeds a minimal DNS packet with a maliciously large Length header into Message.Unpack(). Without the fix, this triggers the out-of-bounds slice panic during the second pass. With the fix, it safely returns a parsing error.
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ISMAIL GAMAL (Gerrit)
ISMAIL GAMAL added 1 comment![]( "Open in Gerrit")
Hi @dn...@google.com @se...@liao.dev @ia...@golang.org,
Just a friendly ping on this CL. I added the requested test case in the latest patchset to verify the boundary check.
Could someone please trigger the TryBots for this when you have a moment? Let me know if there is anything else needed from my end to get this ready for merge.
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